What is resisting ordinary treatment; difficult of fusion, reduction, or the like; -- said especially of metals and the like, which do not readily yield to heat, or to the hammer; as, a refractory ore called?

refractory — Resisting ordinary treatment; difficult of fusion, reduction, or the like; -- said especially of metals and the like, which do not readily yield to heat, or to the hammer; as, a refractory ore. (Webster's 1913.)

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